As therapeutic agents for diabetes, various biguanide type and sulfonylurea type compounds have been used so far. However, the biguanide type compounds cause the lactic acid acidosis and the sulfonylurea type compounds cause serious hypoglycemia posing a problem on their adverse effect, thus the advent of therapeutic agent for diabetes without such defect is desired.
On the other hand, it has been made clear that the aldose reductase takes part in the crisis of diabetic complication (J. H. Kinoshita et al, J. Am. Med. Assoc. 246, 257 (1981)). Thus inhibition of the aldose reductase may bring prevention and therapy of diseases occurring as diabetic complications.
Compounds possessing blood sugar-lowering action and compounds possessing inhibitory action of aldose reductase have been extensively searched each separately, and, with regard to particular thiazolidine-2,4-dione derivatives, compounds having aldose reductase-inhibitory action or blood sugar-lowering action are known.
For example, as the aldose reductase-inhibitory agents, particular thiazolidine-2,4-dione derivatives are already publicly known (Japanese Unexamined Patent Publication No. Sho 57-28073, Chem. Pharm. Bull. 30(10), 3601, (1982)). Namely, it is publicly known that 5-phenylthiazolidine-2,4-dione derivatives represented by a general formula ##STR2## [wherein R denotes a hydrogen atom, lower alkyl group, hydroxyl group, alkoxy group, nitro group, amino group, lower acylamino group, halogen or trifluoromethyl group], have aldose reductase-inhibitory action.
However, thiazolidine-2,4-dione derivatives of the present invention represented by a general formula (1) ##STR3## [wherein R.sup.1 and R.sup.2 each independently represent hydrogen atoms, halogens, lower alkyl groups, hydroxyl groups, lower alkoxy groups, nitro groups or amino groups (said amino group may be substituted with lower alkyl group or lower alkanoyl group), R.sup.3 denotes a hydrogen atom or lower alkyl group, A denotes a lower alkylene or carbonyl group, and B and W denote differently lower alkylenes, carbonyl groups or bonding hands], were not known at all, and also it could not be anticipated that thiazolidine-2,4-dione derivatives of the present invention had superior blood sugar-lowering action together with strong aldose reductase-inhibitory action.
The purpose of the present invention is to provide compounds having superior blood sugar-lowering action and simultaneously strong aldose reductase-inhibitory action and being useful as effective and highly-safe drugs capable of preventing and treating diabetes and complication thereof.